Preparation of aromatic sulfohalides

Abstract

A process for the preparation of aromatic sulfohalides by reacting an aqueous solution, containing a hydrogen halide, of an aromatic diazonium halide with sulfur dioxide, wherein (a) the aqueous solution, containing the hydrogen halide, of a diazonium salt which is derived from the corresponding aromatic amine and the halogen of the desired sulfohalide is reacted with sulfur dioxide in the presence of an inert organic solvent which is immiscible or only partially miscible with water, (b) the diazonium salt is decomposed, simultaneously or subsequently, by means of a catalyst for diazonium salt decomposition and (c) the resulting reaction mixture, or the organic phase thereof after removal of the aqueous phase, is treated with an oxidizing agent.

We claim: 
     
       1. A process for the preparation of an aromatic sulfohalide by reacting an aqueous solution, containing a hydrogen halide, of an aromatic diazonium halide with sulfur dioxide, which process comprises: (a) reacting (1) an aqueous solution which does not dissolve sulfur dioxide, said solution essentially containing the hydrogen halide HX of a diazonium salt which is derived from the corresponding aromatic amine and the halogen X of the desired sulfohalide, with   (2) sulfur dioxide in the presence of an inert organic solvent which dissolves the sulfur dioxide but which is immiscible or only partially miscible with water;     (b) decomposing the diazonium salt, simultaneously or subsequently, by means of a catalyst for diazonium salt decomposition; and   (c) treating the resulting reaction mixture, or the organic phase thereof after removal of the aqueous phase, with an oxidizing agent.   
     
     
       2. A process as claimed in claim 1, wherein the organic solvent used is an aliphatic ketone of 4-10 carbon atoms. 
     
     
       3. A process as claimed in claim 1, wherein the organic solvent used is an aliphatic chlorohydrocarbon of 1-4 carbon atoms, which contains one or two Cl atoms per carbon atom. 
     
     
       4. A process as claimed in claim 1, wherein CuCl 2  or Cu 2  Cl 2  is used as the catalyst for diazonium salt decomposition. 
     
     
       5. A process as claimed in claim 4, wherein a surfactant is used additionally to the copper salt for decomposing the diazonium salt. 
     
     
       6. A process as claimed in claim 5, wherein a surface-active quaternary ammonium salt is used as the surfactant. 
     
     
       7. A process as claimed in claim 1, wherein a surface-active quaternary ammonium salt is used as the catalyst for diazonium salt decomposition. 
     
     
       8. A process as claimed in claim 1, wherein chlorine gas is used as the oxidizing agent. 
     
     
       9. A process as claimed in claim 1, wherein hydrogen peroxide is used as the oxidizing agent. 
     
     
       10. A process as claimed in claim 1 wherein the aromatic amine has the formula   Ar(NH.sub.2).sub.n     where Ar is unsubstituted aryl or aryl bearing inert substituents, said aryl being selected from the group consisting of benzene, naphthalene, pyridine and quinoline, and n is 1 or 2, and where the corresponding sulfohalide product has the formula     Ar(SO.sub.2 X).sub.n     wherein Ar and n have the same meaning given above and X is halogen.